Question

C# allows you to define an implicit cast to a delegate type:

class myclass
{
    public static implicit operator Func<String, int>(myclass x)
    {
        return s => 5;
    }
    public static implicit operator myclass(Func<String, int> f)
    {
        return new myclass();
    }
}

But unfortunately, we can’t use this to make an object look like a function:

var xx = new myclass();
int j = xx("foo");    // error
Action<Func<String, int>> foo = arg => { };
foo(xx);              // ok

Is there a nice way to make an object of one’s own class accept function-style parameters (arguments) directly on of its base instance? Kind of like an indexer, but with parentheses instead of square brackets?

Answer 1

No, C# does not allow that as part of the language. Underneath the covers, the CLI uses the call and callvirt instructions to invoke a method or, indirectly, a delegate.

So, unlike Python where you can make an instance of a class callable by declaring a def __call__ method, C# has no similar feature.